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What is tonicity? IV fluids?

- measure of the effective osmotic pressure gradient of 2 solns measured by a semipermeable membrane - measured in mOsm/Liter
- fluids are:
isotonic if b/t 240-340 mOsm/L
hypotonic if less than 240
hypertonic if more than 340


Fluid compartments in the body?

- intracellular:: in osmotic equilibrium in normal circumstances (28 L)
- extracellular:
intravascular: aka plasma 0 fluid contained within circ and lymphatic system (3.5 L)
- interstitial: fluid that is found outside the circulatory/lymphatic system that surround tissues (10.5 L)
- 3rd space: spaces where fluid does not normally collect in large acts..CSF, joint spaces, vitreous humor, peritoneal cavity


What are colloids?

- fluids containing larger MW (greater than 8000) proteins and molecules with plasma oncotic pressures similar to normal plasma proteins
- large molecules that don't pass through cell membranes
- when infused, they remain in the intravascular compartment and expand the intravascular volume and they draw fluid from extravascular spaces via their higher oncotic pressure
- used as volume expanders:
plasma protein fraction: plasmanate
synthetic colloids: dextran, hetastarch


What are crystalloids?

- fluids with molecular wt of less than 8000, and low oncotic pressure: hypotonic, isotonic, and hypertonic
- contain small molecules that flow more easily across the cell membranes, allowing for transfer from the bloodstream into the cells and body tissues
- this will increase fluid volume in both the interstitial and intravascular spaces


Diff types of crystalloid groups?

- hypotonic: soln of lower osmotic pressure than blood
- isotonic: noting or pertaining to soln containing some salt concentration as blood
- hypertonic: soln higher osmotic pressure than blood


What are hypotonic crystalloids and what will they cause? Used for? Types?

- soln of lower osmotic pressure than blood, osmolality less than 240 mOsm/L
- will cause fluids to leave vasculature for the interstitial ad intracellular spaces
- used for conditions causing intracellular dehydration when fluid needs to be shifted into cells such as:
hyperosmolar hyperglycemic state
- IV fluids:
0.45% NS (1/2 NS)
D5W (after infusing) - isotonic until infused and then body metabolizes glucose very quickly
- these solns will hydrate cells although their use may deplete fluid within the circulatory system


Types of hypotonic fluids?

- 0.45% NaCl (0.45% NS), 0.33% NS, 0.2 NS, and 2.5% dextrose in water


What are the precautions when using hypotonic fluids?

- never give hypotonic fluids to pts with increased ICP b/c it may exacerbate cerebral edema
- don't use solns in pts with liver disease, trauma, or burns due to potential for depleteion of intravascular fluid volume
- the decrease in vasc bed volume can worsen existing hypovolemia and hypotension and cause CV collapse
- monitor pts for signs and sxs of fluid vol deficit
- in older adult pts confusion may be an indicator of a fluid volume deficit, make sure pts know to tell you when they don't feel right


What are isotonic crystalloids? Types? Purpose?

- contain same salt concentration as blood
- doesn't result in any significant fluid shifts across cellular or vascular membranes
- increases vascular volume

- IV fluids
0.9% NS
LRs - burn protocol
D5W (before infusion)


What are hypertonic crystalloids? Types? purpose?

- soln of higher osmotic pressure than blood, greater than 340 mOsm/L.
- will draw fluids from the cells and interstitial spaces into vasculature.
- Used as volume expanders!!

- IV fluids:
7.5% NS: used for pts in critical situations of severe hyponatremia, pts with cerebral edema
D5 in 1/2 NS
dextrose 5% in NS - replaces sodium, chloride and some calories
dextrose 10%


Precautions in hypertonic solns?

- Should only be admin in high acuity areas with constant nursing surveillance for potentiatl complications
- maintain vigilance when admin hypertonic saline solns because of their potential for causing intravascular fluid volume overload and pulmonary edema
- Shouldn't be given for an indefinite period of time
- Rxs for their use should state that specific hypertonic fluid to be infused, the total vol to be infused, the total volume to be infused and infusion rate, or length of time to continue the infusion
- it is better to store hypertonic NS solns apart from regular floor stock of IV fluids


Where will D5W fluids end up?LR, NS? 7.5% saline? 5% albumin? whole blood?

- D5W: majority in intracellular
- NS or LR: take 100 ml out of cells, 825 ml interstitial and then 275 ml into plasma
- 7.5% saline - take out 2950 ml from intracellular, move to interstitial and plasma
- 5% albumin: 500 ml interstitial and 500 plasma
- whole blood: 1000 ml into plasma


What is impt to remember when giving fluids?

- pick approp IV therapy for pt
- pt's underlying illness, VS, serum electrolytes and a host of other variable must be considered
- trying to return or keep body in homeostasis
- Must balance all of the fluid compartments


2 main categories of IV fluid therapy?

- maintenance therapy
- replacement therapy:
mechanical imbalances - hypotension due to hemorrhage, hypotension due to anesthesia, excess fluid loss due to V/D or decreased oral intake
electrolyte imbalances


What is the primary manager of body fluid levels?

- kidneys
- underlying renal disease complicates things
- poor renal perfusion complicates things


What is the most osmotically active electrolyte in the body?

- Na+


What should you take note of when determining fluid status?

- urine output
- serum sodium
- urine osmolality (urine Na)
- edema and BP are impt but don't replace the above!!!!
- take orthostatic vital signs


Maintenance therapy?

- replaces normal ongoing losses
- usually undertaken when the individual isn't expected to eat or drink normally for a longer time (perioperatively, or pt on a ventilator)


What does fluid resuscitation do?

- corrects any existing water and electrolyte deficits


Goal of maintenance therapy? Monitoring?

- goal: preserve water and electrolyte balance
- daily wts are easiest way to monitor net gain/loss of fluids
- normal serum Na+ tells you the pt has adequate water balance but not volume balance
- normal adults have obligate fluid loss of 1600 ml/day


What is the IV fluid usually used for maintenance therapy?

- 0.45% NS + 20 mEq KCl
- think about how water requirement increases 100-150 ml/day for each degree fever greater than 37 C


Goals for replacement or resuscitation therapy?

- goal: correct existing abnormalities in plasma and volume status
- type of fluid given is determined by type lost and current electrolytes
- generally when hypovolemia occurs - the kidneys conserve Na+ and water:
this will be seen as increased serum Na
will be seen earliest as decreased urine Na (less than 25 mEq/L)
- normal BUN/creatinine ratio is 10:1, with hypovolemia this will increase to greater than 20:1


Hypovolemia and metabolic situations?

- ABGs: tells you if pt is acidodic to alkalotic
- with excessive vomiting or NG suction, the pt loses H+ and may develop metabolic alkalosis and hypovolemia
- with excessive diarrhea, the pt may lose Na bicarb and may develop metabolic acidosis and hypovolemia


What is occuring with hemorrhage or trauma?

- this results in loss of circulating blood, hypovolemia, and shock
- hypotension with general anesthesia isn't due to loss of volume, it is due to loss of vascular tone


What is good replacement tx of hypovolemia due to decreased intake or excess excretion (sweating or hung-over)?

- 0.45% NS until labs are back
- if Na is greater than 145 change to 0.25 NS
- if Na is less than 138 cahnge to 0.9 NS
- initially run at 125 ml/hr unless hemodynamically unstable
- monitor electrolytes and vitals
- gross est. of renal perfusion is to make 30 ml/hr (minimum) urine


Tx for hypovolemia due to vomiting or diarrhea?

- 0.9% NS until labs are back
- if serum Na is greater than 145 change to 0.45% ns
- initially run at 125 ml/hr unless hemo unstable
- monitor electrolytes and vitals
- gross est of renal perfusion is to make 30 ml/hr urine


Replacement therapy for hypovolemia due to hemorrhage?

- pt will be tachycardic, tachypneic, systolic BP less than 90, pale, cool, clammy, confused, may be cyanotic
- bolus 1-2 L 0.9% NS or LR through large bore IVs until labs are back
- continue fluid resuscitation based on vital signs and urine output
- packed RBCs as soon as available: type and cross 2 units of PRBCs
- monitor electrolytes, ABGs and vitals
- gross est of renal perfusion is to make 30 ml/hr min urine


Tx of hypovolemia due to burns?

-bolus 1-2 L 0.9 NS or LR through large bore IVs until labs back
- continue fluid resuscitation based on vital signs and urine output
- consider albumin early to maintain pressure and limit edema
- monitor electrolytes, ABGs and vitals
- gross est of renal perfusion is to make 30 ml/hr min urine


What are impt parameters used to assess volume deficit?

- 1 blood pressure
- 2 urine output
- 3 JVP
- 4 urine Na concentration


Signs and sxs of hypovolemic shock?

- anxiety and agitation
- confusion
- rapid breathing
- low BP
- rapid pulse, often weak and thready
- cool, pale skin
- decreased or no urine output
- disturbed consciousness
- low body temp